In recent years, as a camera technology advances and the cost decreases, various systems for supporting driving using a vehicle-mounted camera have been developed. Particularly, in a parking support system of a vehicle, by mounting a camera with a wide-angle lens, a driver can park a vehicle while checking an area including a rear blind spot which is difficult to see directly from the driver's seat.
Patent Literature 1 discloses a parking assist device that draws guide lines of a vehicle width in a moving direction (a backward direction) of a vehicle and displays a ladder-shaped diagram, in a superimposed manner, in which the guide lines are connected at intervals of a predetermined distance. The device disclosed in Patent Literature 1 displays an anticipated traveling locus in a superimposed manner, for example, according to a steering angle detected by a steering sensor.
In Patent Literature 2, as a technique of supporting driving at the time of lane change, disclosed is a drive support apparatus that displays a guide line (a transverse line traversing a monitor), in a superimposed manner, at a boundary position of a dangerous area, a caution area, or a safety area on a road surface, decided based on distance or relative speed.
Meanwhile, as another system using a vehicle-mounted camera, there is an electronic mirror system. The electronic mirror system displays, on a monitor inside a vehicle, a side rear image obtained by capturing a status of an area from the side to the rear (hereinafter referred to as “side rear”) which has been conventionally checked by exterior rear view mirrors or the eyes. In the past, the driver has turned his/her neck or waste at a large angle to check the side mirror or check the side rear in the eyes. However, in the electronic mirror system, the driver can check the side rear by checking a display near the driver's seat. Further, by using the wide-angle lens and arranging the monitor near the field of front vision, even at the time of lane change, safety of the side rear can be checked by checking the electronic mirror near the field of front vision.
However, in the electronic mirror system, the side rear image displayed on the monitor is poorer in stereoscopic effect than a virtual image of the side rear seen through the side mirror, and it is difficult to measure the distance from a vehicle in an adjacent lane by merely displaying the captured image. At the time of lane change, it is necessary to instantly learn the presence and absence of vehicles in an adjacent lane, the distance from other vehicles, and the speed of other vehicles relative to the subject vehicle.
In Patent Literature 3, disclosed is a drive support apparatus that helps a driver to determine the distance by displaying a mark representing a degree of risk from a subject vehicle from the driver's point of view on the side rear image or a mark at the rear position of a predetermined distance. In the device disclosed in Patent Literature 3, it is possible to almost accurately recognize the distance from the subject vehicle to other vehicles by reading the mark that is displayed in a superimposed manner near other vehicles reflected on the side rear image when seeing the side rear image.